301 lines
6.1 KiB
C
301 lines
6.1 KiB
C
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#include <stdlib.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <math.h>
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// Accuracy here matters.
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// With a max 25k TDS (i.e. 16 bits input signal signed)
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// this means 6 + 16 == 22.
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// This fits within a 32 bit int
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// and leaves ten bits of head room.
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//
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// For two pole the y0, y1, y2 registers must be 32 bit at least.
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// The new rpi is 64 bit so these have had to have been deliberately set
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// as int32_t to simulate the pic18 `long' type.
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// The short int type on the PIC18 is `int'
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//
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#define BIN_FRACS 6
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// this is a 64 bit machine (the pi)
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//
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int16_t /* squared version of LAG_7_8 */
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two_pole_7_8 ( int16_t input ) {
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static int32_t y1=0,y2=0, x1,x2;
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int32_t * res;
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int32_t y0;
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int32_t x0 = input;
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// x0 times 0.125
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// the minus 3 divides by 8 : DOUBLE POLE
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x0 <<= (BIN_FRACS-3) ; // now all calculations are done times BIN_FRACS^2
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// this works stabley but not well WHY?
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//y0 = x0 + y1-(y1>>3) - ((y2>>1) + (y2>>2) + (y2>>6));
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// should be
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//y0 = x0 + y1+y1-(y1>>2) - (y2>>1 + y2>>2 + y2>>6);
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//
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//
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// OK this works well
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// y0 = x0 + (14.0 / 8.0) * (double) y1 - (49.0/64.0) * (double) y2;
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y0 = x0 +
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// (14.0 / 8.0) * (double) y1
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// this is 7/4
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y1 + y1 - (y1>>2)
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//
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//
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// - (49.0/64.0) * (double) y2;
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//
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- ( (y2>>1) + // half
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(y2>>2) + // quarter
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(y2>>6) ); // 64th
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//
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// y0 = x0/64 + (y1 * 7) / 4 + (y2*49)/64;
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// see what happens when y2>>6 is left out. I theory d.c goes unstable
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// and yes it does! 25AUG2019
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// y0 = x0 + y1-(y1>>3) - (y2>>1 + y2>>2 /* + y2>>6*/);
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y2 = y1;
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y1 = y0;
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x2 = x1;
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x1 = x0;
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//res = (short int *)&y0;
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//res++;
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//printf("y0=%X res should be %X res=%x\n",y0, y0>>16, res);
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//
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// the plus 3 divides by 8
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return y0>>(BIN_FRACS+3); // divide back down for scaling and then divide by 8 filter gain // *res;
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}
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int16_t /* squared version of LAG_7_8 */
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two_pole_7_8_zg ( int16_t input ) { // with zero guard
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static int32_t y1=0,y2=0, x1,x2;
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int32_t * res;
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int32_t y0;
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int32_t x0 = input;
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// x0 times 0.125
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// the minus 3 divides by 8 : DOUBLE POLE
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x0 <<= (BIN_FRACS-3) ; // now all calculations are done times BIN_FRACS^2
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// this works stabley but not well WHY?
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//y0 = x0 + y1-(y1>>3) - ((y2>>1) + (y2>>2) + (y2>>6));
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// should be
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//y0 = x0 + y1+y1-(y1>>2) - (y2>>1 + y2>>2 + y2>>6);
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//
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//
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// OK this works well
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// y0 = x0 + (14.0 / 8.0) * (double) y1 - (49.0/64.0) * (double) y2;
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y0 = (x0>>1) + (x0>>2) + (x0>>6) + (x2>>1) + // 49/64 * x0 + 1/2 * x2
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// (14.0 / 8.0) * (double) y1
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// this is 7/4
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y1 + y1 - (y1>>2)
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//
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//
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// - (49.0/64.0) * (double) y2;
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//
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- ( (y2>>1) + // half
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(y2>>2) + // quarter
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(y2>>6) ); // 64th
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//
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// y0 = x0/64 + (y1 * 7) / 4 + (y2*49)/64;
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// see what happens when y2>>6 is left out. I theory d.c goes unstable
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// and yes it does! 25AUG2019
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// y0 = x0 + y1-(y1>>3) - (y2>>1 + y2>>2 /* + y2>>6*/);
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y2 = y1;
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y1 = y0;
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x2 = x1;
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x1 = x0;
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//res = (short int *)&y0;
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//res++;
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//printf("y0=%X res should be %X res=%x\n",y0, y0>>16, res);
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//
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// the plus 3 divides by 8
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return y0>>(BIN_FRACS+3); // divide back down for scaling and then divide by 8 filter gain // *res;
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}
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#define BIN_FRACS_15_16 9
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// this is a 64 bit machine (the pi)
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//
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int16_t /* squared version of LAG_7_8 */
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two_pole_15_16 ( int16_t input ) {
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static int32_t y1=0,y2=0, x1, x2;
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int32_t * res;
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int32_t y0;
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int32_t x0 = input;
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// x0 times 0.125
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// the minus 3 divides by 8 : DOUBLE POLE
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x0 <<= (BIN_FRACS_15_16) ; // now all calculations are done times BIN_FRACS^2
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y0 = x0 +
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// (30.0 / 16.0) * (double) y1
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// this is 7/8
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y1 + y1 - (y1>>3)
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//
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//
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// - (49.0/64.0) * (double) y2;
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//
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- ( (y2>>1) + // half
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(y2>>2) + // quarter
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(y2>>3) + // eighth
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(y2>>8) // 256th
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);
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y2 = y1;
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y1 = y0;
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// gain of the filter is 256 ((1/16)^2) if x0 is allowed in withiout pre-dividing
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//
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y0 >>= 8;
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return y0>>(BIN_FRACS_15_16); // divide back down for scaling and then divide by 8 filter gain // *res;
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}
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#define RAND_RANGE 500
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#define DC_TERM 1500
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int zero_only_2 ( int input )
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{
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static int x0,x1,x2,x3,x4;
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int res;
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// (z^2+1)^2
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// z^4 z^2 1
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res = input + 2*x2 + x4;
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x4 = x3;
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x3 = x2;
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x2 = x1;
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x1 = input;
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return res/4;
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}
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int zero_only_3 ( int input )
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{
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static int x0,x1,x2,x3,x4;
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static int x5,x6,x7,x8,x9;
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int res;
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// (z^2+1)^3
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// z^6 z^4 2z^3 z^2 2*z 1
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res = input + x2 +2*x3 + x4 +2*x2 + x6;
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x8 = x7;
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x7 = x6;
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x6 = x5;
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x5 = x4;
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x4 = x3;
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x3 = x2;
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x2 = x1;
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x1 = input;
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return res/8;
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}
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int zero_only_4 ( int input )
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{
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static int x0,x1,x2,x3,x4;
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static int x5,x6,x7,x8,x9;
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int res;
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// z^8 2z^6 2z^5 2z^4 4z^3 2z^2 2z^1 + 1
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res = input + 2*x2 +2*x3 + x4 + 4*x5 + 2*x6 + 2*x7 + x8;
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x8 = x7;
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x7 = x6;
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x6 = x5;
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x5 = x4;
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x4 = x3;
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x3 = x2;
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x2 = x1;
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x1 = input;
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return res/16;
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}
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int main () {
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int i, zo2,zo3,zo4;
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int16_t val,res, res34, res78, res78_2, rr, res_1516;
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for (i=0;i<1000;i++) {
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val = sin ( (double)i*10.0 / (3.142 * 2.0) ) * 10.0 + DC_TERM ;
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rr = rand() % (RAND_RANGE*2);
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rr -= RAND_RANGE;
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val += rr;
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// fast sine
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//val = sin ( ((double)i*10.0) / (3.142 * 2.0) ) * 10000;
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res = two_pole_7_8 ( val );
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res_1516 = two_pole_15_16 ( val );
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zo2 = zero_only_2 (val);
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zo3 = zero_only_3 (val);
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zo4 = zero_only_4 (val);
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res34 = (((res34<<2) - res34)>>2) + (val>>2);
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res78 = (((res78<<3) - res78)>>3) + (val>>3);
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res78_2 = (((res78_2<<3) - res78_2)>>3) + (res78>>3); // feed res78 into another should be the same as two pole
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// 1 3 5 7 9 11 13 15 17 19
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printf ("%d val %d res %d res34 %d res78 %d res78_2 %d res_1516 %d zo2 %d zo3 %d zo4 %d EOL\n",
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i, val,res, res34, res78, res78_2, res_1516, zo2, zo3, zo4);
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}
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return 0;
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}
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